The field of this invention relates to an improved process for acidizing oil wells in which asphaltene or other heavy hydrocarbon type deposits are either present or potentially a problem. Thus, this improved process is not only useful in cleaning and stimulating oil wells in which production has been reduced because of the heavier fractions depositing near the face of the wellbore, but it is also useful in preventing such problems when it is known that the presence of an aqueous flush would induce asphaltene precipitation.
In the recently issued U.S. Pat. No. 3,819,520 (incorporated herein by reference), we disclosed and claimed a new acidizing composition with improved oil displacing ability capable of leaving solid surfaces water-wet without forming emulsions. These improved functions were shown to be related to low interfacial tensions between the aqueous acid solution in the presence of the alcohols and a hydrocarbon having from 10 to 12 carbon atoms per molecule. Although the improved acidizing compositions of U.S. Pat. No. 3,819,520 are useful in stimulating many wells and, in principle, should lead to improved oil displacement in all applications, certain problem wells have remained, stubbornly resisting all attempts to restore them to their original production flow rates. In particular, wells which are producing from formations containing crude oil having a high concentration of asphaltenes and other heavy hydrocarbon components tend to form a "skin" at or near the wellbore which will not dissolve in the alcohol-acidizing process. In solving this problem, we have discovered an improved method of using the alcohol-acidizing composition claimed in U.S. Pat. No. 3,819,520 which cleans and stimulates such problem wells. In one notable instance, a well which had for over four years resisted all attempts to stimulate production was virtually restored to its original state by our improved process.